Fuel cell is an effective device that can convert the chemical energy to the electric energy through the electro-catalytic reactions. The proton exchange membrane fuel cell (PEMFC) operates at a relatively low temperature with the gas phase hydrogen as fuel and oxygen (air) as oxidant. Due to its high conversion efficiency, low noise and low emissions, PEMFC is deemed with high potential in automobile and distributed power generation.
At the core of a PEMFC is the membrane electrode assembly (MEA) which consists of an anode, a cathode and a polymer electrolyte layer in between. At the surface of the anode, hydrogen is oxidized to proton through the electro-catalytic processH2→2H++2e−  (1)
The protons thus produced are transported to the cathode side through the proton conductive membrane. At the surface of the cathode, oxygen is electro-catalytically reduced and subsequently reacts with protons from the equation (1) to form waterO2+4e−+4H+→2H2O  (2)
The reaction (2) is also known as the oxygen reduction reaction (ORR). The reactions (1) and (2) occur on the surface of the electrode catalysts. At present, the most effective catalyst for these reactions are made of platinum supported on the amorphous carbon. A typical Pt loading on the MEA surface ranges from 0.2 mg/cm2 to 0.4 mg/cm2. Since platinum is a precious metal with limited supply, its usage adds a significant cost to a PEMFC system. Other platinum group metals (PGMs), such as Pd, Rh, Ru, etc., are also being evaluated as the replacement for Pt. They too, suffer the issues on the high cost and limited reserves.
Cathodic oxygen reduction reaction, such as that described by the Equation 2, typically occurs at the surface of platinum in the electro-catalyst. Molecular oxygen is first adsorbed on the Pt active site and is subsequently converted to the water by capturing four electrons and reacting with four protons. Few catalyst metals were found to have a comparable catalytic efficiency as that of platinum for the ORR. Those found with similar catalytic activity usually belongs to the precious group metals (PGM), such as Pd, Rh, Ir, Ru, etc., in addition to Pt. The PGMs generally carry high price due to limited reserve worldwide. The use of PGMs in an electrochemical device such as fuel cell will add significant cost to the system therefore creating major barrier for commercialization. For example, a typical polymer electrolyte fuel cell (PEFC) contains 0.2 mgPt/cm2 or higher at the cathode side of the membrane electrode assembly. It is highly desirable to find the method to prepare the electrode catalyst at significantly reduced PGMs usage in fuel cell and similar electrocatalytic application.